Compressed loads with long bullets

[Marvsehn@aol.com]

I built my Grendel about 18 months ago and have reloaded most the the 1000 rounds fired so far. I was chasing my concern about load compression when I started inspecting my loads for long bullets more closely. Take for instance the Hornady 123 SST, 129 SST and the Barnes 127 LRX. All are boat tail and plastic tip and about 1.3 inches + long.

Let's take the Hornady rounds. I have Hornady load data and for the 129 SST. Which has a COL listed at 2.245" and a max load of CFE223 at 31.7 grain.

But here is what I encounter when loading the case with 31.7 grain. When I put the bullet in the case (testing with a once fired case) on this powder load the COL is 2.390" when pushed down by hand as much as I could. In order to get to the recommended Hornady COL of 2.245" I need to compress .150 (150 thousands).

When backing off to 30.0 grain the COL is reduced to 2.270" which would still require a compression of .030 (30 thousands).

So maybe 30 thousands would be ok but 150 thousands sounds like to much. The case available to powder would be about 1.15" and if I compress .150" then it could be considered about 13%. or the lesser load of 30 gn would be about 2.6%

Has anyone encountered the compression and how you might measure it.

I have loaded some of the Hornady 123 SST to the max and the numbers look simular to the above. No problems so far, no burnt primers no real case problems. I'm not sure it is an issue. The max Hornady loads just seemed to have more compression than I expected.

I could reduce powder load. Also, could extend the COL to about 2.280" But my real question has to do with to much compression.

Any comments or insight will be greatly appreciated.

[Koda]

Supposedly there is a concern with loads where if the bullet protrudes too far inside the case causes something called a "donut" reducing brass life. Ive never encountered it so I cant say for sure.

I do know less case volume reduces velocity potential, and can increase pressure. Ideally, I try to choose bullets that dont protrude past the case shoulder for any caliber. The Grendel is a short case already, and if your loading to fit an AR magazine you don't have many options to seat a bullet longer than saami max. If you want to use a heavier bullet its a trade off with lower velocity. If a bolt gun, having a smith throat the freebore longer I think would get some great velocity out the Grendel with the longer bullets.

I don't know how to literally measure compression, but I have a trick that lets me seat my longer bullet without compressing the load. Keep in mind that you might not actually be compressing, but rather displacing the powder around the base of the bullet. There are some tricks to helping compress powder before seating. Long powder funnels help compact the powder as its poured in. Ive never used one so cant say how well. Vibration is what works really well for me. The bullet I'm loading is just a bit longer than I would prefer (1.135" long) and just barely protrudes past the lower shoulder jct, before I seat the bullet I hold it against a hand engraver which vibrates the powder compressing it. A .257cal bullet barely slips in a sized grendel case neck and I can watch it move down by about .1" as it vibrates (this is probably the only way to measure powder compression, before and after vibration). After that, the 6.5 bullet seats in without any compressing that I can "feel" when seating. It only takes about 5 seconds to vibrate the powder that way. If you don't have a hand engraver, you can repeatedly tap the case for a while and get the same effect, it just takes too long to be practical.

[Marvsehn@aol.com]

Thanks. I will give that a try. Saw the vibration idea on a few other posts, just didn't think it would shake down that much.

[Marvsehn@aol.com]

Thanks. I will give that a try. Saw the vibration idea on a few other posts, just didn't think it would shake down that much.

So I loaded some and tried the shake down method. Saw another version of it, by taking a tray that holds the brass, load the charge (I did 3, CFE 223, A2520, Varget), then put another tray upside down, on top to hold everything in place. Laid on an oscillator tool for 5 seconds or so.

This used max Hornady load data on a 129g SST.

All shook down so there was no more compression when seating the bullet. Shake down was in the range of .040 to .060.

I am going to the range in the next day.

So, with this shake down, would it be considered compression? We are certainly removing the small gaps.

At least, I have refrained from crunching the power when loading the round.

Thanks for the feedback.

[JASmith]

I have been known to use a battery powered toothbrush for vibrating powder in cases. I contacted the case block with the head of the tooth brush and all the cases vibrated.

(Electric powered guys should work fine to, but I didn't want to mess with cords.)

[Koda]

So I loaded some and tried the shake down method. Saw another version of it, by taking a tray that holds the brass, load the charge (I did 3, CFE 223, A2520, Varget), then put another tray upside down, on top to hold everything in place. Laid on an oscillator tool for 5 seconds or so.

This used max Hornady load data on a 129g SST.

All shook down so there was no more compression when seating the bullet. Shake down was in the range of .040 to .060.

I am going to the range in the next day.

So, with this shake down, would it be considered compression? We are certainly removing the small gaps.

At least, I have refrained from crunching the power when loading the round.

Thanks for the feedback.

excellent news, .04-.06 is significant and eliminated compression. Im glad this worked for you.

IMO, no, vibration is more of a consolidation to me but not a compression, basically a more efficient use of space like a well played game of Tetris. After you seat the bullet, handling the round will re-disperse the powder around the bullet but there is no pressure on the bullet.
Compression breaks apart the powder granules with force making some of them more compact and leaves pressure on the bullet, Ive heard they can push it back out over time.

[Happy2Shoot]

Where is written that "compressed loads" are something to be concerned with? Why do people ask about this? Some reloading books tell you the % compression for each load (Nosler). Powder crunch is nothing new, like 100 years ago nothing new. This question comes up regularly on the reloading forums. There has to be a beginners guide out there that gives bad advice. Just curious Marvsehn, how did you come to think about compressed loads being unsafe?

https://www.nosler.com/308-winchester

Look at 168gr with "Big Game" powder. 111% load density with a spherical powder no less. Not going to vibrate that down. 52.5 grains of powder is a big load. All compressed means is low energy density / slow burn rate, or both.

[Klem]

I agree with Happy here, but I still think we need to be mindful. Especially if doing it for the first time, or loading for long term storage (e.g., prepping). I use compressed loads in other calibres all the time, using standard tricks to increase density like vibrating and drop tubes. After 103% full which is technically already compressed that's when it starts to crunch, and in a small case like the Grendel it doesn't take much more before it starts to get impossible.

[JASmith]

Some folks have written that the crunch sound may indicate that some grains are getting broken. The breakage, if it happens, increases the powder surface area PLUS exposes some parts of powder grains that were previously covered by the inhibitors and other chemicoas that help regulate bur rate and storage characteristics.

[Koda]

OP was able to vibrate his load down so it was no longer compressing, thats a win win to me. Its good to ask questions and I think its normal to be cautious of new steps in reloading. I think people ask about this because intentionally compressing is not intuitive, for me I haven't read anywhere when or why its needed or an accurate way to measure just how much your compressing. At some point you cant fit anymore and too much compression can unseat bullets coal. Its noted in reloading manuals rarely but thats it, and probably rare anyone would have the same cases and components listed. I think its a good question.

[cory]

Compressed loads are very common for me. I also like to experiment with the 140gr and heavier solid bullets. I'll load my rounds within a few hundredths to a tenth of the desired length, I'll use a vibratory case tumbler with the rounds in a reloading tray, and then press the bullets to the final length. I have done this almost exclusively with CFE 223 FWTW.

Now I'm not telling you this is the right way to do it. I don't know if it is or not frankly. I know I haven't had any problems, but I haven't put enough of these rounds down range to know for sure. I don't get to put as many rounds down range these days.